Spinal hydatid cyst initially diagnosed as spinal tumor: A case report and review of the literature

Key Clinical Message The spinal hydatid cyst is a benign pathology but has considerable morbidity. It should be considered as a differential diagnosis in patients having signs and symptoms of spinal compression, particularly in endemic areas.


| INTRODUCTION
Hydatid cyst is a parasitic infectious disease caused by larvae of Echinococcus granulosus cestode. 1 This infection is more prevalent in areas where livestock and agriculture are common. Mortality from this cyst ranges from 0.9% to 3.6%. 2 It can infest all organs and tissues; almost 60%-70% of the hydatid cysts are formed in the liver, while about 15%-20% involve the lungs. Bone involvement is rare and beholds only in around 0.5%-2% of cases, nearly half of which are located in the vertebrae. 1,3 Spinal cord involvement is rare and has a poor prognosis. Mostly, the thoracic vertebra is involved. 4 Clinical symptoms are usually latent and not specific and correlate with the location and size of the lesion. The symptoms may appear when the lesions become large. The symptoms range from radicular pain to bone fractures. 2,5 Generally, we have five locations of spinal hydatid cases described as intramedullary, intradural extramedullary, extradural, vertebral, and paravertebral lesions. 6,7 Surgery is the prior treatment for spinal echinococcosis. Provided that a patient is suspected of this infection, biopsy or aspiration should be avoided due to the diffusion and anaphylaxis risk. 2 This study presents a patient with a spinal hydatid cyst, who was first admitted with a suspicion of a spinal tumor. A narrative review of spinal hydatidosis cases will also be provided.

| CASE PRESENTATION
A 38-year-old Iranian woman with a history of back and chest pain that eventually led to numbness in the abdomen and legs was admitted to Iranmehr Hospital in December 2021. Symptoms developed in 6 months. The patient did not have a pet and had no history of underlying diseases. Her last pregnancy was 7 years ago. The patient had a history of axillary surgery. Her family history revealed that the patient's brother had thoracic hydatid cysts at the age of 40, both of which were pulmonary cysts in different lungs.
The primary diagnosis was a spinal cord tumor at the T5 level, most likely an epidermoid one, since the cyst was not recognized to be echinococcosis with MRI primarily. Components of the cyst in sagittal cross-sections of T5 had caused damage and fracture of the thoracic vertebrae in this area (see Figure 1).
During the surgery, it turned out that the lesion was a hydatid cyst. Thereafter, pathologic investigations confirmed the diagnosis. The report was from an extramedullary intradural specimen. The microscopic finding was acellular lamellated and germinative layers accompanied by some scolices.
The patient underwent surgery, and the cystic lesion was completely removed without any rupture via hemilaminectomy of the T5 vertebrae from the left side. In addition, two-stage combined anterior and posterior decompression was performed. The surgical region was washed off using 20% hypertonic saline during the same session. The patient received albendazole 10-15 mg/kg/ day postoperatively for 6 months. In 6 months of follow-up, the patient had no related complaints, and her back and chest pain resolved.

| DISCUSSION
Echinococcosis is a zoonotic and chronic infection; it occurs worldwide, usually in tropical and subtropical regions. Therefore, it is difficult to determine the exact prevalence and number of infected patients. 2,8 Hydatid infection mainly forms in the liver and lungs, as these organs trap most of the larvae. Spinal hydatid cyst is rare and occurs in fewer than 1% of patients with hydatidosis. In spinal cord involvement, clinical manifestations depend on the level of vertebrae involvement and the stage of the disease. 9,10 The spinal echinococcosis symptoms depend on how much compression applies to the spinal cord. Some nonspecific symptoms include back pain, sensory discomfort, dysuria, etc. Previous studies have demonstrated that patients also suffer from paraplegia. 2,11 Consequently, when a bone is fractured, neurological deficits and pain arise together. 1 A summary of recent studies on spinal hydatid cysts is available in Table 1.
In this case report, our patient had back pain that led to numbness in the abdomen and legs. CT scan and MRI work-ups confirmed a spinal lesion. Although the patient was admitted with spinal tumor diagnosis, other possible differentials were also considered. Highlighting that the patient's family history of infestation was positive, biopsy was not performed. Therefore, the hydatid cyst was not diagnosed till surgery. MRI is the modality of choice in the radiologic examination. However, when the typical appearance is not present, it would lead to misdiagnosis. 12 The gold standard treatment for hydatid cysts is surgery, by eliminating the whole cyst. Therefore, timely and accurate diagnosis results in choosing the best treatment. Even if the patient is doubtful of spinal echinococcosis, biopsy and aspiration of the cyst are not recommended because of diffusion risk and anaphylaxis that might happen. 2,9 Various solutions are used for washing the surgical region, and postoperative adjuvant antiparasitic chemotherapy consists of hypertonic saline (3%, 10%, 20%), 0.5% betadine, 0.5% silver nitrate, and 2% formalin. 1,10 Albendazole pharmacotherapy is recommended after surgery for 6 months to 1 year to prevent any recurrence of the cyst. For our patient, albendazole was prescribed for 6 months under the supervision of an infectious disease specialist.

| CONCLUSIONS
The spinal hydatid cyst is a benign pathology but has considerable morbidity. It should be considered as a differential diagnosis in patients having signs and symptoms of spinal compression, particularly in endemic areas. Furthermore, correct and timely preoperative diagnosis and suitable surgical techniques according to the cyst features are essential in preventing recurrence.